Hi @mreza_kiani – thank you for your interest in this idea!
Plone doesn't use a SQL database, not directly. Plone's storage is done via the ZODB, an object database. It is actually a wonderful architecture and implementation which is in many ways superior to relational databases.
To understand how Plone deletes objects, please see elsewhere in this forum where we describe the idea of implementing the recycle bin GSoC 2022 contribution / recycle bin idea - #2 by tkimnguyen